Carbon dioxide emissions from human activities are acidifying the oceans and threaten a mass extinction of sea life, a top ocean scientist warns.
Dr Carol Turley from Plymouth Marine Laboratory says it is impossible to know how marine life will cope, but she fears many species will not survive.
Since the Industrial Revolution, CO2 emissions have already turned the sea about 30% more acidic, say researchers.
It is more acidic now than it has been for at least 500,000 years, they add.
The problem is set to worsen as emissions of the greenhouse gas increase through the 21st Century.
“I am very worried for ocean ecosystems which are currently productive and diverse,” Carol Turely told BBC News.
“I believe we may be heading for a mass extinction, as the rate of change in the oceans hasn’t been seen since the dinosaurs.
“It may have a major impact on food security. It really is imperative that we cut emissions of CO2.”
Dr Turley is chairing a session on ocean acidification at the Copenhagen Climate Change Congress.